trouble streaming images with send_data

rubyonrails-talk
1

Hi

I'm doing some server-side graphics with Java2D and I'm trying to stream the resulting image to the browser using send_data. When I try to view the image that I streamed, the browser just shows the URL in the window as a very small image (about .4 kb) when I am using jpeg format. For png, it tells me that the image has errors and can't load it.

Here's what I'm doing in the controller:

def sendImage         biFiltered = BI.new(100, 100, BI::TYPE_INT_RGB)         big = biFiltered.createGraphics()         $w = 0         $h = 0         begin         filename = "#{RAILS_ROOT}/public/images/kids.jpg"         imagefile = java.io.File.new(filename)         bi = javax.imageio.ImageIO.read(imagefile) w = bi.getWidth(nil);                 h = bi.getHeight(nil);                 if bi.getType != BI.TYPE_INT_RGB                         bi2 = BI.new(w, h, BI::TYPE_INT_RGB)                         big = bi2.createGraphics()                         $stderr.print "after getting graphics"                         big.drawImage(biFiltered, 0, 0, nil)                         bi = b2                         biFiltered = bi                 end         rescue                 $stderr.print "Couldn't load file"         end

        big.drawImage(biFiltered, java.awt.geom.AffineTransform.getScaleInstance(2, 2), nil)         os = java.io.ByteArrayOutputStream.new         begin                 isWritten = javax.imageio.ImageIO.write(biFiltered, "jpeg", os)         rescue                 $stderr.print "Couldn't write file"         end

        if isWritten            send_data "os.toByteArray", :type => "image/ jpeg", :disposition => "inline", :filename => "scaledkids.jpg" end end

And then in the HTML file, I just point to the sendImage action from an img tag.

Does anyone have advice on this? Should I not use the ByteArrayOutputSteam. It seems that others have used this without problems.

Thanks. JB

2

Hi        if isWritten           send_data "os.toByteArray", :type => "image/ jpeg", :disposition => "inline", :filename => "scaledkids.jpg"

You're just sending the string "os.toByteArray" rather than the actual
image bytes. I haven't the faintest clue what a ByteArrayOutputSteam,
but for it to work with send_date you're going to have to make it look
like a ruby string (which is just a chunk of bytes), i'm sure there's
some jruby cleverness to assist with that sort of thing.

Fred

3

Thank you, Fred. I will look into the ruby string. And sorry, everyone, for posting this message twice--accidentally hit send too soon.

JB

4

According to the following information, I'd have to do some array allocation/copying or something like that to write Java output streams directly to the backing byte array of Ruby strings because this doesn't seem to have been implemented yet?

http://jira.codehaus.org/browse/JRUBY-929

Could anyone give me a hint on how to perform the workaround?

Thanks

5

This is just a guess based on 5 minutes of looking at the jruby wiki,
but http://wiki.jruby.org/wiki/Calling_Java_from_JRuby#Ruby_String_to_Java_Bytes_and_back_again   might be interesting.

Fred